* private field 'netif' is not used [clang-diagnostic-unused-private-field]
* private field 'instance' is not used [clang-diagnostic-unused-private-field]
* Call to virtual method 'FdTerminal::stop' during destruction bypasses virtual dispatch [clang-analyzer-optin.cplusplus.VirtualCall]
* unused variable 'TAG' [clang-diagnostic-unused-const-variable]
* Null pointer passed as 2nd argument to memory copy function [clang-analyzer-unix.cstring.NullArg]
* Array access (from variable 'data') results in a null pointer dereference [clang-analyzer-core.NullDereference]
This change is needed for the fs terminal to work correctly again, after
merging 44bae24c78 which shifted
responsibility of thread safety from a terminal to the DTE. (Before it
was the terminal, which removed this callback safely when processing completed,
and thus we had to check the callback return value). Not the DTE layers
are responsible for thread safety and the return value indicates
success/failure from processing.
Also uses the default clock, the same way as UART terminal.
